If this is 5.0, can you go to the VM view in the Inventory, expand the Resource table and then toggle to the Constraint view. Let's see what this view shows if both clusters are represented as "Constrained By"

If you do not see the other cluster, let's review the diagnostics to see that this VM is buying from both clusters and somehow does not have a constraint on it. In fact I think you already opened a support ticket?

There are 2 WorkloadPlacementPoliccy's. the first one tells the VM to run on BB_Test (=003_Oracle). And the second tells that the VM should place on specific datastores (both clusters see the same datastores).

correct I opened also a ticket: #5997

I didn't recocnized the "Constrains" at VM Views in the past. Is very usefull!